Device for controlling the hardness of water supplied to a washing machine, in particular a dish-washing machine

Abstract

 The device comprises a solenoid valve of the proportional type (5), connected to the decalcifying device (3) and able to control the flow of water supplied to the washing chamber or tank (WT), and a control unit (CU, 7) able to drive said proportional solenoid valve (5) in a predetermined manner in such a way as to cause variations in the flowrate of the water supplied to the washing chamber or tank (WT), causing corresponding variations in the hardness of the water flow supplied to said chamber or tank (WT).

Description

[0001] The present invention relates to a device for controlling the hardness of the water supplied to the washing chamber or tank of a washing machine, in particular a dish-washing machine.

[0002] More specifically, the invention relates to a control device comprising:

a water supply pipe connected to the washing chamber or tank of the machine, and

a decalcifying device arranged along said supply pipe.

[0003] One object of the present invention is to provide an improved device for controlling the hardness of water supplied to a washing machine, able in particular to keep the hardness value of the water supplied to the washing chamber or tank substantially at a predefined ideal value.

[0004] This object, together with others, is achieved according to the invention by a device for controlling the hardness of the water, characterized in that it comprises:

at least one solenoid valve of the proportional type, connected to the decalcifying device and able to control the flow of water supplied to said washing chamber or tank; and

control means able to drive said at least one solenoid valve in a predetermined manner in such a way as to cause variations in the flowrate of the water supplied to the washing chamber or tank and cause corresponding variations in the hardness of the water flow supplied to said chamber or tank.

[0005] In a first embodiment, the device according to the invention comprises a proportional solenoid valve connected hydraulically in series with the decalcifying device.

[0006] In an alternative embodiment, the device comprises a plurality (for example two) proportional solenoid valves connected hydraulically in parallel with each other and in series with the decalcifying device, these solenoid valves preferably having different respective maximum flowrate capacities (for example 1 litre/minute and 2 litres/minute).

[0007] Further characteristic features and advantages of the present invention will emerge from the detailed description which follows, provided solely by way of a non-limiting example with reference to the accompanying drawings in which:

Figure 1 is a Cartesian graph which shows the progression of the hardness D_out of the water at the outlet of the decalcifying device, as a function of the quantity Q of water supplied to the washing chamber or tank;

Figure 2 is a Cartesian graph which shows the progression of the hardness of the water D_out of the water at the outlet of the decalcifying device, as a function of the instantaneous flowrate Q_inst of the water supplied to the washing chamber or tank; and

Figure 3 is a schematic representation, partly in the form of blocks, of a first device for controlling the hardness of the water according to the present invention;

Figure 4 is a diagram of a variation of embodiment of the control device according to the invention;

Figure 5 is a schematic illustration of a further variation of embodiment of the device according to the invention; and

Figure 6 is a schematic illustration of still another variation of embodiment.

[0008] Figure 1 of the accompanying drawings is a diagram which shows, in qualitative terms, the progression of the hardness D_out of the water at the outlet of a decalcifying device for a washing machine, in particular a dish-washing machine, as a function of the flowrate Q (measured for example in litres) of water supplied to the washing chamber or tank. The decalcifying device to which the graph according to Figure 1 refers is of the type currently used in dish-washing machines (ion-exchange resin decalcifier).

[0009] The curve indicated by A in the diagram of Figure 1 shows the progression of the hardness of the water D_out upon variation in the (overall) flowrate Q of the water supplied to the washing chamber for a given constant value D_in1 of the hardness of the water D_in at the inlet of the decalcifier.

[0010] The broken-line curves B and C show the progression of the hardness D_out upon variation in the flowrate Q, for two different values D_in2 and D_in3, respectively, of the hardness of the water D_in at the inlet of the decalcifier, with D_in1 < D_in2 < D_in3.

[0011] The diagram of Figure 1 shows a constant level Did of the hardness D_out, this constant level representing an ideal level of hardness of the water in order to avoid for example, in a dish-washing machine, the deterioration of glass or crystal crockery, such as glasses, which is likely to occur when the hardness of the water is too low.

[0012] The device for controlling the hardness of the water according to the invention is designed so as to tend to keep the hardness of the water which is supplied to the washing machine or chamber of a washing machine substantially constant and equal to a predefined ideal value D_id.

[0013] Figure 2 of the accompanying drawings shows a further graph which illustrates, in qualitative terms, the progression of the hardness of the water D_out at the outlet of a decalcifying device, as a function of the instantaneous water flowrate Q_inst (measured for example in litres/minute).

[0014] As shown in the graph according to Figure 2, the hardness D_out is a substantially increasing function of the instantaneous flowrate Q_inst.

[0015] Figure 3 shows a first embodiment of a device according to the present invention. This device, which is denoted overall by 1, essentially comprises a water supply pipe 2 with an inlet end 2a operationally connected to a supply source, such as a normal water distribution network, and an outlet end 2b connected to the washing chamber or tank WT of a washing machine, in particular a dish-washing machine of the type known per se.

[0016] 3 denotes a decalcifying device, which is likewise of a type known per se, arranged along the supply pipe 2.

[0017] A so-called "air break" device 4 is arranged along the pipe 2, upstream of the decalcifier 3.

[0018] In the embodiment shown in Figure 3, the control device 1 according to the invention comprises a solenoid valve 5 of the proportional type, associated with the decalcifying device 3 and in particular connected hydraulically in series with the latter, upstream of the air break device 4.

[0019] The proportional solenoid valve 5 is driven by a control unit CU and also acts as a solenoid valve for introducing the water.

[0020] In the embodiment shown, the decalcifying device 3 has, associated with it, a sensor device 7 able to provide the control unit CU with signals indicating the hardness of the water in this decalcifying device.

[0021] During operation, the flow of water necessary for the machine reaches the washing chamber or tank WT via the proportional solenoid valve 5 and the decalcifying device 3.

[0022] Via the proportional solenoid valve 5, the control unit CU is therefore able to vary the flowrate of the water supplied to the washing chamber WT and, in accordance with the graph shown in Figure 2, control correspondingly the hardness of the water flow supplied to the said washing chamber or tank.

[0023] Figure 4 shows another embodiment of the control device according to the invention which exploits the dependency of the hardness D_out at the outlet of a decalcifier upon variation in the instantaneous flowrate Q_inst of the water passing through it.

[0024] In the embodiment according to Figure 4, parts and components already described have been denoted again by the same reference numbers used before.

[0025] The variant according to Figure 4 illustrates a plurality (in particular two) proportional solenoid valves 5 and 5a which are arranged hydraulically in parallel with each other and in series with the decalcifier 3, upstream of the blow-off device 4.

[0026] The control unit CU is designed to drive selectively these proportional solenoid valves 5, 5a so as to cause (when necessary) variations in the instantaneous flowrate of the water through the decalcifier 3, causing consequently also a corresponding variation in the hardness of the water D_out at the outlet of the latter and therefore at the inlet of the washing chamber or tank WT.

[0027] Conveniently, the solenoid valves 5, 5a ... have respective different respective maximum flowrate capacities, for example 1 litre/minute and 2 litres/minute, so that by means of coordinated driving thereof, it is possible to vary the overall flowrate between zero and 3 litres/minute.

[0028] Figure 5 shows a further variation of embodiment in which, upstream of the decalcifier (resin tank) 3, an overflow or breather tube 6 extends upwards from the pipe 2 with its top end rising above the tank WT of the washing bath. The height of the tube 6 is selected so that, in the case of low water flowrate values, the backpressure created by the decalcifier 3 is insufficient to cause overflowing of water from the tube 6 towards the tank WT, while, in the case of a flowrates which are higher (than a predetermined threshold), said overflowing occurs, in an increasingly marked manner with an increase in the flowrate. The water overflowing from the duct 6 is not decalcified and is mixed with the water of the washing bath contained inside the tank WT, varying the hardness thereof.

[0029] The duct 6 therefore introduces a further method of varying the hardness of the washing bath water.

[0030] In figure 6 there is shown another variant of embodiment. In that Figure parts and elements which had already been described have been attributed again the reference numerals previously used.

[0031] In the variant according to Figure 6 there is no air break device immediately downstream of the solenoid valve 5. The function of such an air break is unified with that of overflow or breather tube 6 which operates as a backflow stopper.

[0032] The variant according to Figure 6 allows to minimize the flow resistance, and therefore the flow rate at low pressures is increased. Furthermore, downstreams of the device 6 the hydraulic pressure is practically equal to zero. The noise generated in the water-loading phases is reduced. Moreover, the backflow stopper does not generate air bubbles and therefore air does not flow through the softener. Finally, the number of components is reduced.

[0033] Also in the device according to Figure 5 or 6, in place of a single proportional solenoid valve 5, it is possible to envisage a plurality of said valves as described above in connection with Figure 4.

[0034] The embodiments shown in the figures described above are of the closed-loop, namely feedback type: the control unit CU is designed to drive the proportional solenoid valve or valves 5 or 5, 5a according to the hardness of the water detected by the sensor 7.

[0035] The scope of the present invention also includes similar embodiments, not shown, in which there is no water hardness sensor such as that indicated by 7 in Figures 3 to 6, but in which the control system is essentially of the open loop type. In these devices (not shown) the control unit CU has, conveniently connected thereto, a setting device which can be manually operated by the user and is able to provide the control unit CU with signals indicating the (known) hardness of the water distributed by the local water mains. The unit CU is thus designed to drive subsequently, during operation of the machine, the proportional solenoid valve 5 in such a way as to keep the hardness of the water inside the chamber or tank WT at a substantially constant level, depending on the local hardness of the water set by the user.

[0036] The devices for controlling the hardness of the water according to the invention have a notable structural simplicity and operate in a reliable and safe manner.

[0037] Moreover, with these devices, it is possible to reduce the quantity of ion-exchange resins in the decalcifying device: by reducing the flowrate of the water supplied to the decalcifying device, it is possible to reduce in any case the hardness to the desired constant ideal value, even though there is an increase in the time required for filling the washing chamber or tank WT with the necessary quantity of water.

[0038] A further advantage consists in the fact that "washing" of the resins in the decalcifier, performed with a low water flow, allows a reduction in the consumption.

[0039] Finally, it is possible to obtain with the devices according to the invention, by means of special programming of the control unit, a washing bath having a different hardness depending on the washing cycle performed and/or varying during various stages of a same washing cycle.

[0040] In all the above-described embodiments of the invention the control is performed in an "open loop", i.e. without using sensors or transducers which provide the control unit with an accurate indication of the magnitude of the water flow through the proportional electrovalve(s). For an optimum operation it is however preferable to perform the control in a "closed loop", i.e. using a flow rate sensor or transducer (of a per se known type) adapted to provide the control unit with a signal indicative of the instantaneous water flow rate, being it possible to position such a sensor or transducer either downstream or upstream of the proportional electrovalve(s) used.

[0041] Obviously, without affecting the principle of the invention, the embodiments and the constructional details may be widely varied with respect to that described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the accompanying claims.

Claims

1. Device for controlling the hardness of the water supplied to the washing chamber or tank (WT) of a washing machine, in particular a dish-washing machine, comprising:

a water supply pipe (2) connected to the washing chamber or tank (WT) of the machine; and

a decalcifying device (3) arranged along said water supply pipe (2);

the control device being characterized in that it comprises:

a solenoid valve of the proportional type (5), connected to the decalcifying device (3) and able to control the flow of water supplied to said washing chamber or tank (WT); and

control means (CU, 7) able to drive said proportional solenoid valve (5) in a predetermined manner in such a way as to cause variations in the flowrate of the water supplied to the washing chamber or tank (WT), causing corresponding variations in the hardness of the water flow supplied to said chamber or tank (WT).

2. Control device according to Claim 1, in which said proportional solenoid valve (5) is connected hydraulically in series with the decalcifying device (3).

3. Control device according to Claim 1 or 2, comprising a plurality of proportional solenoid valves (5, 5a) which are connected hydraulically in parallel with each other and in series with the decalcifying device.

4. Control device according to Claim 3, in which said proportional solenoid valves (5, 5a) have respective different maximum flowrate capacities.

5. Control device according to one of the preceding claims, in which, upstream of the decalcifier device (3), there is provided a breather or overflow tube (6) which extends from said water supply pipe (2) and which has a height such that it is able to allow the overflow of non-decalcified water towards the washing chamber or tank (WT) when the water flowrate in said supply pipe (2) exceeds a predetermined value.

6. Control device according to any one of the preceding claims, in which said control means comprise:

sensor means (7) able to provide signals indicating the hardness of the water at the outlet of the decalcifying device (3), and

a control unit (CU) designed to drive said proportional solenoid valve (5) depending on the signals supplied by said sensor means (7).

7. Control device according to any one of Claims 1 to 5, in which said control means comprise:

setting means able to provide signals indicating the level of hardness of the water adopted for said supply pipe (2), and

a control unit (CU) designed to drive said proportional solenoid valve (5) depending on the signals supplied by said setting means.

8. Control device according to any one of the preceding claims, in which said control means (CU) are designed to drive said at least one proportional solenoid valve (5; 5, 5a) in such a way that inside the washing machine there is a washing bath with a hardness which depends on the washing cycle performed and/or the stage of the washing cycle performed.

9. Control device according to any of the preceding claims, comprising further sensor means capable of providing the control means (CU, 7) with electrical signals indicative of the water flow rate through the proportional electrovalve(s) (5, 5a).

Drawing